The use of ink-jet printers to form images such as alphanumeric characters and graphics on absorbent substrates such as paper is well-known.
However, the use of the same inks on non-ink receptive substrates, such as polyester films, commonly known as Mylar, has not produced the same high density of print, which results in intense colors, obtained with inherently absorbent substrates. Such non-ink receptive substrates do not readily absorb the aqueous-based inks commonly employed in ink-jet printing, with the result that dots of ink do not spread laterally and are slow to dry. For the purposes of this disclosure, the term "non-ink receptive substrates" is used to describe those substrates comprising materials which drops of ink deposited thereon do not penetrate.
Attempts have been made to remedy the situations in which ink-jet images on non-ink receptive substrates, such as transparencies, are slow to dry or lack capacity to absorb sufficient volumes of ink, with a goal of approaching performance obtained with highly absorbent, porous media. One such attempt is described in a technical paper by D. R. Titterington et al, "Development of a Transparent Receiving Sheet for Ink-Jet Printing", Journal of Imaging Science, Vol. 30, No. 1, pp. 4-8 (Jan/Feb 1986); see also U.S. Pat. No. 4,503,111. This reference describes the use of certain transparent hydrophilic coatings to permit the use of aqueous-based inks for printing on transparent media. However, the reference mostly addresses the problem of slow drying of transparencies. It does not disclose ways to improve image density.
While such coatings are useful, considerable work remains to be done to develop suitable inks and coatings and methods of application that permit substantially uniform high color density images to be produced on non-ink receptive substrates, whether transparent or otherwise, approaching that which can be produced on ink-receptive substrates, such as paper.
Often, it is desired to store printed images, such as transparencies, by insertion into removable, clear plastic sheet protectors of a type that allow filing in a 3-ring binder. Such sheet protectors can be removed for projection. However, most such protective holders, when used soon after printing images on ink-receptive coatings formed on non-ink receptive substrates, cause problems such as image smearing due to trapped ink vehicle.
Thus, a need remains to develop improved ways for generating stable images on non-ink receptive substrates, such as overhead transparency projections, using ink-jet printing methods.